Systems and methods for intraoperatively measuring anatomical orientation

ABSTRACT

Systems and methods are disclosed in which changes in the position and/or orientation of an anatomical structure or of a surgical tool can be measured quantitatively during surgery. In some embodiments, a surgical electronic module can be configured to attach to a surgical device, to continually detect changes in a position and/or orientation of the surgical device during surgery, and to communicate the changes to a user. In this way, where the surgical device is attached to a portion of a patient&#39;s anatomy and/or is used to manipulate the patient&#39;s anatomy, the surgical electronic module can detect changes in the position and/or orientation of said anatomy. In embodiments where more than one module is used during surgery, the modules can continually detect changes in their positions and/or orientations relative to one another, which correspond to changes in relative positions and/or orientations of the surgical devices to which the modules are attached.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/471,120 filed on Aug. 28, 2014, which is hereby incorporated byreference in its entirety.

FIELD

The present disclosure is related to systems and methods for measuringanatomical position and/or orientation. In some embodiments, systems andmethods quantitatively measure changes in the position and/ororientation of a portion of a patient's anatomy with respect to anotherportion of the patient's anatomy during surgery.

BACKGROUND

Many surgical procedures require a surgeon to intraoperatively assesschanges in the position or orientation of one or more portions of apatient's anatomy. However, even in open surgeries, there can beobstructions that prevent a surgeon from viewing relevant anatomy at asurgical site, e.g., blood, adjacent soft tissue, etc. Traditionalsurgical procedures use imaging techniques, such as CT-scans, x-rays,etc., to pre-operatively plan for a desired anatomical correction andthen to post-operatively assess whether the desired anatomicalcorrection has been achieved. Viewing the anatomical changesintraoperatively using such imaging techniques can be difficult,however, as it may require interruption of the surgery. Also, manyimaging techniques only provide snapshots illustrating progressivechanges in a qualitative manner, but do not provide data of changes asthey occur in real-time. A further limitation of such imaging techniquesis that they may only provide qualitative data, thus requiring a surgeonto make a subjective assessment of when a desired anatomical orientationhas been achieved. Such imaging techniques also expose the patient andthe operating room staff to potentially-harmful radiation.

During a traditional pedicle subtraction osteotomy, surgeons remove bonefrom a vertebra of a patient suffering from a spinal deformity tocorrect spinal curvature. To intraoperatively determine when theappropriate amount of bone has been removed, the surgeon must be able toaccurately assess the amount of correction that has been achieved at agiven time. Traditionally, to make this assessment, the surgeon muststep back from the surgical procedure while an imaging device is broughtin and positioned to view the curvature of the spine. However, thisprovides only a subjective measure of angular correction and involves aninterruption in the surgical procedure, adding time and inconvenience.Often times, this results in sub-optimal patient outcomes and repeatsurgeries due to over- or under-correction of the deformity.

Thus, there is a need for improved systems and methods forintraoperatively measuring anatomical position and/or orientation.

SUMMARY

Systems and methods are disclosed in which changes in the positionand/or orientation of an anatomical structure or of a surgical tool canbe measured quantitatively during surgery. In some embodiments, asurgical electronic module can be configured to attach to a portion of apatient's anatomy and/or to a surgical device, to continually detectchanges in a position and/or orientation of the patient's anatomy and/orthe surgical device during surgery, and to communicate the changes to auser. Where the surgical device is attached to a portion of a patient'sanatomy and/or is used to manipulate the patient's anatomy, the surgicalelectronic module can detect changes in the position and/or orientationof said anatomy. In embodiments where more than one module is usedduring surgery, the modules can continually detect changes in theirpositions and/or orientations relative to one another, which correspondto changes in relative positions and/or orientations of portions of thepatient's anatomy and/or the surgical devices to which the modules areattached.

In one exemplary embodiment, a surgical electronic module is providedthat includes a housing having one or more engagement features that areconfigured to removably attach the housing to a surgical device, asensor, a processor, and a display. The sensor can be disposed in thehousing and can be configured to detect a position or orientation of themodule with respect to the earth. The processor can be coupled to thesensor and can be configured to calculate a change in position ororientation of the surgical device with respect to one or more referencepoints when the surgical device is attached to the module, based on theposition or orientation detected by the sensor. The display can beconfigured to display the change calculated by the processor to therebyassist a user in assessing changes in position or orientation of anatomycoupled to or manipulated by the surgical device. In some embodiments,the display can be disposed on the housing.

In some embodiments, the surgical electronic module can includeadditional components. By way of non-limiting example, the surgicalelectronic module can further include a reset mechanism that, whenactuated, sets an initial position or orientation of the module to beused in calculating the change in the position or orientation of thesurgical device. Additionally or alternatively, the surgical electronicmodule can include a memory configured to store at least one of theposition or orientation detected by the sensor and the change calculatedby the processor. In still further embodiments, the surgical electronicmodule can include a communications interface configured to send theposition or orientation detected by the sensor to an external device andto receive a position or orientation of the one or more reference pointsfrom the external device. The external device can be a second surgicalelectronic module.

In some embodiments, the one or more reference points can include asecond surgical electronic module. In some embodiments, the sensor canbe configured to detect the position or orientation at predeterminedtime intervals and/or the processor can be configured to calculate thechange at the predetermined time intervals. The processor can further beconfigured to calculate first, second, and/or third derivatives of theposition or orientation of the surgical device. In still furtherembodiments, the one or more engagement features can be configured toidentify an aspect of the surgical device when the surgical device isattached to the module.

In another aspect, a surgical method is provided for measuring a changein anatomical position or orientation. The method can involve detectingan absolute angle of a first electronic module attached to a firstsurgical device by a sensor of the first electronic module, with thefirst surgical device being operatively coupled with a first portion ofa patient's anatomy and detecting an absolute angle of a secondelectronic module attached to a second surgical device by a sensor ofthe second electronic module, with the second surgical device beingoperatively coupled with a second portion of the patient's anatomy. Themethod can also include calculating by a processor of at least one ofthe first and second electronic modules a change in an angle of thefirst electronic module with respect to the second electronic modulemultiple times during a surgery to determine a change in an angle of thefirst surgical device with respect to the second surgical device. Themethod can further include conveying to a user the change in the angleof the first surgical device with respect to the second surgical deviceto thereby assist the user in determining a change in an angle of thefirst portion of the patient's anatomy with respect to the secondportion of the patient's anatomy. In some embodiments, the change in theangle of the first surgical device with respect to the second surgicaldevice is conveyed to the user on a display of at least one of the firstelectronic module and the second electronic module.

In some embodiments, the method can further include actuating resetmechanisms of the first and second electronic modules to set an initialangle of the first module with respect to the second module. The initialangle can be used in calculating the change in the angle of the modulesrelative to one another. The calculating and the displaying steps can berepeated until a target position or orientation of the first surgicaldevice with respect to the second surgical device has been reached. Insuch embodiments, the method can further include alerting the user whenthe target position or orientation has been reached. In still furtherembodiments, the method can include calculating a rate of the change inthe angle of the first surgical device with respect to the secondsurgical device.

In some embodiments, the first and second portions of the patient'sanatomy are first and second vertebra on opposite sides of an osteotomysite. When the first portion of the patient's anatomy is a firstvertebra and the first surgical device is a first bone screw implantedin the first vertebra, the method can further include attaching thefirst electronic module to the first bone screw. Additionally, when thesecond portion of the patient's anatomy is a second vertebra disposedopposite an osteotomy site from the first vertebra and the secondsurgical device is a second bone screw implanted in the second vertebra,the method can further include attaching the second electronic module tothe second bone screw. In such embodiments, the method can also includelocking a spinal rod to the first and second bone screws after a targetposition or orientation of the first vertebra with respect to the secondvertebra has been reached.

In yet another aspect, a surgical method is provided for guiding asurgical instrument. The method can include detecting an orientation ofa first electronic module that is attached to the surgical instrument bya sensor of the first electronic module, detecting a position of thefirst electronic module via communications between the first electronicmodule and at least two electronic modules attached to at least twosurgical devices, calculating by a processor of the first electronicmodule a change in the orientation of the surgical instrument and achange in the position of the surgical instrument over time, andconveying to a user the change in the orientation and the position ofthe surgical instrument to thereby assist the user in guiding thesurgical instrument during surgery. In some embodiments, the change inthe position and the orientation of the surgical instrument is conveyedto the user on a display of the first electronic module. In someembodiments, the at least two surgical devices do not move with respectto a patient's anatomy while the user is guiding the surgicalinstrument.

The present invention further provides devices and methods as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a schematic illustration of a spherical coordinate system;

FIG. 1B is a schematic illustration of relevant anatomical planes;

FIG. 2 is a schematic illustration of an exemplary surgical electronicmodule;

FIG. 3 is a perspective view of the surgical electronic module of FIG.2;

FIG. 4 is a perspective view of a spine of a patient with a spinaldeformity;

FIG. 5 is a perspective view of one step of an exemplary method forcorrecting spinal deformity using surgical electronic modules;

FIG. 6 is a perspective view of another step of the method of FIG. 5;

FIG. 7 is a perspective view of one step of another exemplary method forcorrecting spinal deformity using surgical electronic modules; and

FIG. 8 is a perspective view of another step of the method of FIG. 7.

DETAILED DESCRIPTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of skilled in the art will understand that the devicesand methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

In the present disclosure, like-numbered components of the embodimentsgenerally have similar features and/or purposes. Further, to the extentthat linear or circular dimensions are used in the description of thedisclosed systems, devices, and methods, such dimensions are notintended to limit the types of shapes that can be used in conjunctionwith such systems, devices, and methods. A person skilled in the artwill recognize that an equivalent to such linear and circular dimensionscan easily be determined for any geometric shape. Sizes and shapes ofthe systems and devices, and the components thereof, can depend at leaston the size and shape of the components with which the systems anddevices are being used, the anatomy of the patient, and the methods andprocedures in which the systems and devices will be used. The figuresprovided herein are not necessarily to scale.

Systems and methods are disclosed in which changes in a position and/ororientation of an anatomical structure or of a surgical tool can bemeasured quantitatively during surgery. In some embodiments, a surgicalelectronic module can be configured to attach to a surgical device, tocontinually detect changes in a position and/or orientation of thesurgical device during surgery, and to communicate the changes to auser. In this way, where the surgical device is attached to a portion ofa patient's anatomy and/or is used to manipulate the patient's anatomy,the surgical electronic module can detect changes in the position and/ororientation of said anatomy. In embodiments where more than one moduleis used during surgery, the modules can continually detect changes intheir positions and/or orientations relative to one another, whichcorrespond to changes in relative positions and/or orientations of thesurgical devices to which the modules are attached. Additionally oralternatively, at least one of the modules can help to establish areference 3D location in the operating room, particularly where the atleast one of the modules is stationary. In some embodiments, the modulescan include a resetting or “zeroing” function that allows a user toselectively set an initial relative position and/or orientation of themodules to zero. Subsequent changes in the relative positions and/ororientations of the modules can then be measured and displayed to theuser so that the user knows when a desired change in position and/ororientation of the modules has been reached. In some embodiments, all ofthe components necessary for detecting, calculating, and/orcommunicating positional information (i.e., position and/or orientation)are contained within the module itself, thus eliminating the need for anexternal base station or other additional bulky equipment. By thusproviding a means for quantitatively measuring changes in anatomicalorientation in real-time during surgery, exemplary systems and methodsprovided herein can enhance the accuracy of the surgery and reduce oreliminate the need for intraoperative imaging, thereby reducingradiation exposure and increasing efficiency.

The positional information detected and/or calculated by the surgicalelectronic module can include one or more angles of the module withrespect to the earth (referred to hereinafter as “absolute” angles), oneor more angles of the module with respect to a some other referencepoint (referred to hereinafter as “relative” angles), distances betweenthe module and one or more external reference points, changes in any ofthese values, a rate of changes in any of these values, and/or higherorder derivatives of any of these values. The module can be configuredto detect and/or calculate the positional information in a variety ofunits and coordinate systems. To provide relevant anatomicalmeasurements during surgery, in some embodiments the module can beconfigured to translate positions and/or orientations detected in aspherical coordinate system, illustrated in FIG. 1A and defined by anabsolute azimuth angle θ, an absolute polar angle φ, and a radialdistance r, into positions and/or orientations along the sagittal,axial, and coronal planes, illustrated in FIG. 1B.

The surgical electronic module can include one or more components fordetecting, processing, communicating, and/or storing positionalinformation of the module and the surgical device to which it isattached. As schematically illustrated in FIG. 2, an exemplary module 10can include a processor 22, a memory 24, a communications interface 26,and a sensor 28—all of which can be in communication with each other.Any of these components can exist external to the module 10, however,for example at a remote base station configured to communicate with themodule 10 through the communications interface 26. Further, althougheach of these components are referred to in the singular, it will beappreciated by a person skilled in the art that the various functionsdescribed as being carried out by one of the components can actually becarried out by multiple of those components, e.g., the functionsdescribed as being carried out by the processor 22 can be carried out bymultiple processors. The electrical components can be powered by abattery contained within the module 10, for example a lithium ionbattery, or can be powered by an external power source coupled to themodule 10 via an adaptor.

The sensor 28 can be or can include any type of sensor that isconfigured to detect positional information of the module 10. By way ofnon-limiting example, the sensor 28 can include an accelerometer (e.g.,a 9-axis accelerometer for measuring one or more angles of the module 10with respect to a reference point such as the earth), a gyroscopicsensor, a geomagnetic sensor, and the like. Additionally oralternatively, where the module 10 is configured to detect a distance ofthe module from a reference point, the sensor 28 can include ultrasound,electromagnetic, and/or infrared transceivers for communicating with apositioning system. In an exemplary embodiment, the sensor 28 can beconfigured to detect an absolute position and/or orientation of themodule in the spherical coordinate system. The sensor 28 can beconfigured to detect the positional information at intervals throughouta surgical procedure, for example every second, every millisecond, everymicrosecond, etc., such that the positional information is effectivelydetected continuously and in real-time. The positional information canbe detected regularly, intermittently, or at non-regular intervals. Thepositional information can be conveyed to the surgeon, stored in thememory 24, conveyed to the processor 22 for processing, and/orcommunicated to one or more external devices via the communicationsinterface 26 for processing or storage.

Where the sensor 28 is configured to detect both an orientation and aposition (e.g., a distance of the module 10 from some reference point),the module 10 can be configured to switch between an orientationdetection mode in which the sensor 28 detects only the orientation and afull detection mode in which the sensor 28 detects both the orientationand the position. The module 10 can be configured to switch between theorientation detection mode and the full detection mode at the request ofthe surgeon, for example via actuation of an input device on the module10, and/or based on an identity of the surgical device to which themodule 10 is attached.

The processor 22 can include a microcontroller, a microcomputer, aprogrammable logic controller (PLC), a field-programmable gate array(FPGA), an application specific integrated circuit (ASIC), integratedcircuits generally referred to in the art as a computer, and otherprogrammable circuits, and these terms are used interchangeably herein.The processor 22 can be configured to generate positional informationand/or perform various calculations based on the positional informationdetected by the sensor 28, stored in the memory 24, and/or received froman external device via the communications interface 26. By way ofnon-limiting example, the processor 22 can be configured to calculate arelative position and/or orientation of the module 10 with respect to anexternal reference point based on an absolute position and/ororientation of the module 10 that is detected by the sensor 28 and/or anabsolute position and/or orientation of the external reference pointthat is received through the communications interface 26. The processor22 can be configured to calculate changes in the absolute and relativepositions and/or orientations of the module 10 and/or a speed at whichthose changes occur, which will correspond to changes and/or a speed ofthe surgical device to which the module 10 is attached.

The processor 22 can be coupled to the memory 24, which can include arandom access memory (RAM), a read-only memory (ROM), a flash memory, anon-transitory computer readable storage medium, and so forth. Thememory 24 can store instructions for execution by the processor 22 toimplement the systems disclosed herein or to execute the methodsdisclosed herein. Additionally or alternatively, the memory 24 can storethe positional information sensed by the sensor 28, calculated by theprocessor 22, and/or received from an external device through thecommunications interface 26.

The communications interface 26 can be configured to receive andtransmit information from any of the processor 22, the memory 24, andthe sensor 28 with one or more external devices, e.g., another surgicalelectronic module, a base station, etc. The communications interface 26be wireless (e.g., near-field communication (NFC), Wi-Fi, Bluetooth,Bluetooth LE, ZigBee, and the like) or wired (e.g., USB or Ethernet). Inthe case of NFC, for example, the module 10 can include a radiotransceiver configured to communicate with a radio transceiver ofanother device, e.g., a second module, using one or more standards suchas ISO/IEC 14443, FeliCa, ISO/IEC 18092, and those defined by the NFCForum. The communication interface 26 can be selected to provide thedesired communication range. In some embodiments, Bluetooth (e.g., class2 Bluetooth having a range of 5-10 meters) can be used for thecommunication interface to allow the module 10 to remain somewhatdistant from the device with which it is communicating, e.g., the secondmodule and/or a base station, while at the same time limiting thecommunication range such that other mobile devices unlikely to be usedin the surgery are not needlessly involved.

As shown in FIG. 3, the exemplary module 10 can include a proximalhousing 20 and a distal shaft 30. In general, the housing 20 and theshaft 30 can be any size and shape configured to be inserted at leastpartially into a patient's body during surgery while not substantiallyobstructing a surgeon's view of or access to a surgical site. Any or allof the above described components for detecting, processing, and/orcommunicating positional information can be housed within the housing20. Further, the housing 20 can have various external features forinputting and outputting the positional information, for example thehousing 20 can include an electronic display 50 for communicatinginformation detected and/or calculated by the module 10 and/or a zeroingbutton 60 to allow the user to indicate that the module 10 is in aninitial position and/or orientation. The shaft 30 can extend distallyfrom the housing 20 and can be configured to rigidly and mechanicallyattach the module 10 to the surgical device such that changes in theposition and/or orientation of the surgical device result incorresponding changes in the position and/or orientation of the module10.

The display 50 can be configured to communicate the positionalinformation detected and/or calculated by the module 10 to assist thesurgeon in assessing anatomical changes effected by the surgical deviceto which the module 10 is attached. In the illustrated embodiment, thedisplay 50 is formed on a proximal-facing surface of the housing 20,although the display 50 can be located anywhere on the module 10, e.g.,such that it is visible to the surgeon during surgery, or it can belocated remotely from the module. The display 50 can be any type ofdisplay screen, e.g., liquid crystal, light emitting diode, etc., and insome embodiments can be configured to withstand exposure tosterilization, liquids, and/or high levels of moisture. In an exemplaryembodiment, the display 50 can display a change in the absolute orrelative position and/or orientation of the module 10 during surgery,which corresponds to a change in the position and/or orientation of thesurgical device to which the module 10 is attached. In some embodiments,the display 50 can additionally or alternatively provide positive and/ornegative feedback to the surgeon about the position and/or orientationof the module 10. By way of non-limiting example, when the module 10detects that a desired position and/or orientation has been reached, thedisplay 50 can provide positive feedback to the surgeon, e.g., a greenlight. When the module 10 is determined to be outside a desirablepositional range, the display 50 can provide negative feedback to thesurgeon, e.g., a red light, an error message, etc. Other means forcommunicating information to the surgeon can include, withoutlimitation, a vibrator, a speaker or buzzer for providing audio feedbackand an internal or external display in communication with the module 10for providing visual feedback. The external display can be larger thanthe display 50 and, in some embodiments, can provide a real-timegraphical illustration of the movement of the module 10 and optionallyone or more other modules during surgery.

The positional information output by the module 10, for example on thedisplay 50, can be reset to zero at any time by user actuation of aresetting or “zeroing” mechanism to thereby indicate that the module 10is in an initial position and/or orientation. For example, a positionand/or orientation of the module 10 displayed at a starting point of thesurgery can to be set to zero upon actuation of the zeroing button 60 bythe surgeon, although it will be appreciated by a person skilled in theart that the zeroing mechanism can be any feature on the module 10 or itcan be remote to the module 10. After the zeroing button 60 has beenpressed, the display 50 can display a change in the position and/ororientation of the module 10 relative to a zero position and/ororientation, such that the surgeon can readily know the differencebetween the initial position and/or orientation of the module 10 and acurrent position and/or orientation of the module 10. Thus, where thesurgery requires changing a position and/or orientation of a patient'sanatomy that is connected to the module 10 via the surgical device by adesired amount, the surgeon can know that the desired change has beeneffected when the desired change of the module 10 is displayed on thedisplay 50. In some embodiments, actuation of the button 60 can alsoinitiate detection and/or calculation of the position and/or orientationof the module 10.

The module 10 can be configured to attach directly to a patient'sanatomy and/or to the surgical device via one or more engagementfeatures 40 formed on a distal portion of the module 10, for example onthe distal end of the shaft 30. The surgical device can be anything usedin the operating room that facilitates the surgery, including, by way ofnon-limiting example, surgical implants, surgical instruments, fixturesin the operating room, e.g., an operating table, etc. The engagementfeatures 40 can be specifically configured to mate the module 10 only toa single type of surgical device, or they can be adaptable or modular toallow for mating of the module 10 to any of a variety of surgicaldevices. Further, the engagement features 40 can be configured to matethe module 10 to more than one surgical device at a time. The engagementfeatures 40 can provide for direct rigid mechanical attachment of themodule 10 to the surgical device to thereby ensure that changes in aposition and/or orientation of the surgical device result incorresponding changes in the position and/or orientation of the module10. In some embodiments, the engagement features 40 can be configured torigidly attach to engagement features of another surgical electronicmodule to calibrate the module 10 with the other surgical electronicmodule, e.g., by synchronizing coordinate systems. Non-limiting examplesof engagement features 40 include a snap mechanism, a lock-and-keymechanism, an electronic contact, a screw or other threaded feature,etc.

In some embodiments, the engagement features 40 can be configured todetect identification information about the surgical device to which themodule 10 is attached. For example, the engagement features 40 cancomprise one or more buttons, switches, pressure transducers, etc. thatare configured to align with one or more protrusions on the surgicaldevice. The number and arrangement of protrusions can serve to uniquelyidentify the surgical device. In this way, the number and arrangement ofbuttons or other components that are engaged by the one or moreprotrusions on the surgical device can convey identification informationabout the surgical device. In another embodiment, the engagementfeatures 40 can include a radio frequency identification (RFID)transceiver or optical scanner that is configured to read a uniquedevice identifier (UDI) contained in either an RFID tag or bar code,respectively, on the surgical device. The identification information caninclude a type of the surgical device, a serial number of the surgicaldevice, an angle at which the surgical device is configured to attach tothe module 10, an age of the surgical device, an intended use of thesurgical device, etc.

The identification information can be conveyed to the surgeon, forexample to ensure that the module 10 has been securely attached to thecorrect surgical device. Where the module 10 is determined not to havebeen attached to the correct surgical device, the module 10 can alertthe surgeon to the error, for example by displaying an error message onthe display 50. In some embodiments, where the identificationinformation includes an angular offset of a portion of the surgicaldevice from the module 10 when the surgical device is attached to themodule 10, the identification information can be used to calculate anabsolute position and/or orientation of that portion of the surgicaldevice. Additionally or alternatively, the identification information,e.g., a type of the surgical device, can cause the module 10 to detectand/or calculate different types of positional information. By way ofnon-limiting example, the module 10 can be configured to switch into thefull detection mode when the engagement features 40 detect that themodule 10 is connected to a surgical instrument that is intended tochange position and orientation during surgery, and into the orientationdetection mode when the engagement features 40 detect that the module 10is connected to a surgical device, e.g., an implant, that is only orprimarily intended to change orientation during the surgery. In stillfurther embodiments, where the module 10 is in communication with anexternal display that provides a graphical depiction of the surgery inreal-time based on positional information transmitted from the module10, the external display can use the identification information toincorporate an illustration of the surgical device to which the module10 is attached in the graphical depiction. The identificationinformation can be stored along with positional information collectedand/or calculated by the module 10 during surgery, e.g., to facilitatelater reconstruction of the surgery.

The surgical electronic modules disclosed herein can generally be usedto detect a position and/or orientation of a surgical device to whichthey are attached as well as changes in said position and/ororientation. Where the surgical device is also attached to a portion ofa patient's anatomy, the surgical electronic module can be used todetect a position and/or orientation of that portion of the patient'sanatomy as well as changes in said position and/or orientation. In anexemplary embodiment, two surgical electronic modules can be attached totwo pedicle screws to detect an amount of correction in a patient'sspinal curvature during a pedicle subtraction osteotomy.

The steps of an exemplary pedicle subtraction osteotomy utilizing themodule 10 and a second module 10 a, which can be identical to the module10, are illustrated in FIGS. 4-6. However, it will be appreciated by aperson skilled in the art that any surgical electronic module asdescribed herein can be used, either the same or different from oneanother, and that the modules 10, 10 a can be used in a variety ofsurgical procedures that effect changes in anatomical position and/ororientation. Further, it will be appreciated that the calculations saidto be performed by the modules 10, 10 a can either be performed by bothof the processors 22, 22 a or by only one of the processors 22, 22 a.Where the below-described calculations are performed by both of theprocessors 22, 22 a, the modules 10, 10 a can communicate the results ofthe calculations with one another to check for accuracy and can displayan error message to the user when there is a mismatch. The calculationscan also be performed by a remote base station configured to receivepositional information from the modules 10, 10 a.

As shown in FIG. 4, prior to the exemplary osteotomy procedure, thepatient's lumbar spine includes a kyphotic deformity in which a firstvertebra V1 is positioned at an angle a in the sagittal plane relativeto a second vertebra V2. A purpose of the osteotomy procedure can be toreduce the angle a to a desired value, e.g., by removing a correspondingamount of bone from a vertebra disposed between the vertebrae V1, V2.The amount of angular correction can be determined based onpre-operative imaging and calculations. In some embodiments, prior tosurgery, the modules 10, 10 a can be calibrated to one another tothereby synchronize their coordinate systems. For example, the modules10, 10 a can be mechanically connected to one another via, e.g., theengagement features 40, 40 a, and rotated through space as a pair untilsufficient information has been gathered to synchronize their coordinatesystems. An output signal can be provided to the user, for example avisual signal on the display 50, a vibration, and/or an audio signal, toindicate when synchronization has been completed. Such synchronizationcan facilitate automated error correction, e.g., for axial rotations,and/or can facilitate quantification of coronal plane changes.

First and second pedicle screws 70, 70 a can be implanted into first andsecond pedicles P1 and P2 of first and second vertebrae V1 and V2, asshown in FIG. 5, according to customary surgical procedures. The firstmodule 10 can be rigidly attached to the first pedicle screw 70 and thesecond module 10 a can be rigidly attached to the second pedicle screw70 a via the engagement features 40, 40 a of the first and secondmodules 10, 10 a. The modules 10, 10 a can be attached to the pediclescrews 70, 70 a either before or after the pedicle screws are implanted.Through this series of connections, changes in the positions and/ororientations of the first and second modules 10, 10 a can correspond tochanges in positions and/or orientations of the first and second pediclescrews 70, 70 a, respectively, and to changes in positions and/ororientations of the first and second pedicles P1, P2 to which thepedicle screws 70, 70 a are attached.

Once the modules 10, 10 a have been attached to the screws 70, 70 a andthe screws 70, 70 a have been implanted in the pedicles P1, P2 in aninitial position and/or orientation, the modules can be powered up andthe zeroing buttons 60, 60 a can be actuated to indicate to the modules10, 10 a that the modules 10, 10 a are in the initial position and/ororientation. Thus, as shown in FIG. 5, the displays 50, 50 a can eachdisplay “0” to indicate that the modules 10, 10 a are oriented at aninitial angle relative to one another. As the procedure is performed,the sensors 28, 28 a of the modules 10, 10 a can detect absolute azimuthand polar angles θ, φ of each of the modules 10, 10 a with respect tothe earth. The modules 10, 10 a can communicate their absolute azimuthand polar angles θ, φ to one other via the communications interfaces 26,26 a. Given this information, the processors 22, 22 a can then calculatea relative angle β of the first module 10 with respect to the secondmodule 10 a in the sagittal plane (e.g., by subtracting the absoluteangles measured by the modules). The relative angle β at the initialposition and/or orientation of the modules 10, 10 a can be stored in thememories 24, 24 a.

Angular correction of the spine along the sagittal plane can then beperformed according to customary surgical procedures, which can includeremoval of bone between the first and second vertebrae V1, V2 at anosteotomy site O of a vertebra disposed between the vertebrae V1, V2.During the correction, the sensors 28, 28 a can continually detect theabsolute azimuth and polar angles θ, φ of the modules 10, 10 a and theprocessors 22, 22 a can continually calculate the relative angle β basedon the updated azimuth and polar angles θ, φ. As the relative angle βchanges during the surgery, the processors 22, 22 a can furthercalculate a change Δβ in the relative angle β over a specified period oftime. In the illustrated embodiment, where the modules 10, 10 a werezeroed at the initial position and/or orientation, the change Δβ in therelative angle β between the initial angle and the current angle (andthus the amount of correction achieved) can be displayed on the displays50, 50 a. In this way, the user can be provided with a real-time,quantitative measurement of angular correction throughout the surgery.When the desired angular correction has been achieved (FIG. 6), asindicated for example by the value of Δβ displayed on the displays 50,50 a, the patient's spine can be stabilized in the corrected positionand/or orientation.

In some embodiments, the processors 22, 22 a can further calculatederivatives of values detected by the sensors 28, 28 a and/or calculatedby the processors 22, 22 a, such as β, θ, and φ. By way of non-limitingexample, the processors 22, 22 a can calculate a first derivative of β,i.e., a rate of change Δβ/Δt in the relative angle β over time, a secondderivative of β, i.e., a relative acceleration Δβ/Δt², and/or a thirdderivative of β, i.e., a relative jerk Δβ/Δt³ of the modules 10, 10 aThe rates of change Δβ/Δt, Δθ/Δt and/or Δφ/Δt can be useful for errorchecking, for example to indicate whether the patient has beenaccidentally moved during the procedure. For example, in embodimentswhere the processors 22, 22 a calculate a rate of change Δθ/Δt for eachof the modules 10, 10 a, it can be assumed that the patient is movingwhen the rate of change Δθ/Δt of the first module 10 is equal to therate of change Δθ/Δt of the second module 10 a, since it is unlikelythat the first and second modules 10, 10 a would be moved at preciselythe same rate as part of the surgical procedure. Thus, when the rate ofchange Δθ/Δt of the first module 10 is equal, or at least substantiallyequal, to the rate of change Δθ/Δt of the second module 10 a, either orboth modules 10, 10 a can alert the surgeon to the patient's movement,for example by displaying an error message on the displays 50, 50 a.Additionally or alternatively, to provide clinical feedback, the ratesof change Δβ/Δt, Δθ/Δt and/or Δφ/Δt can be displayed, e.g., on thedisplays 50, 50 a, and/or stored, e.g., in the memories 24, 24 a.Information about the rates of change Δβ/Δt, Δθ/Δt and/or Δφ/Δt can beuseful for clinicians because they provide a measure of how quickly ananatomical adjustment is made, which may correlate to patient outcomes.

In some embodiments, spinal fixation or stabilization hardware (e.g.,screws and rods) can be coupled to a first side of the patient's spinebefore correction is performed without locking down the fixationhardware. The modules can be coupled to screws implanted in a second,contralateral side of the patient's spine. After the desired amount ofcorrection is achieved, the fixation hardware in the first side of thepatient's spine can be locked down to maintain the corrected angle. Themodules can then be removed and a spinal fixation element 80 can beattached to the pedicle screws 70, 70 a implanted in the second,contralateral side to complete the fixation. In other embodiments,spinal fixation or stabilization hardware can be coupled only to asingle side of the patient's spine, e.g., a side on which the modules10, 10 a are attached. It will be appreciated that the modules 10, 10 acan be removed from the pedicle screws 70, 70 a either before or after aspinal fixation element or rod 80 is coupled to the pedicle screws.

The above-described method involves a single level osteotomy and firstand second modules 10, 10 a configured to measure a local correction,however it will be appreciated that more complex deformity correctioncan also be performed. For example, rotational deformities or angulardeformities in any of the sagittal, axial, and/or coronal planes can becorrected and the degree of correction monitored using the modulesdisclosed herein. By way of further example, several modules (e.g.,three, four, five, six, seven, eight, or more) can be coupled tocorresponding vertebrae to provide correction measurements for a spinalsegment (e.g., a lumbar region, a thoracic region, a cervical region,etc.) or for an entire spine (e.g., from skull to tailbone). Measurementdata associated with such procedures can be communicated to an externaldisplay to give the surgeon a graphical depiction of overall spinalcorrection.

Although not shown, additional information can be displayed on thedisplays 50, 50 a and/or on an external display in communication withthe modules 10, 10 a. The information displayed on the display 50 can beselected by a user before the procedure, can be impacted by the surgicaldevice to which the module 10 is attached, and/or can be preconfiguredas part of the factory settings of the module 10. By way of non-limitingexample, the modules 10, 10 a can convey positive and/or negativefeedback to the surgeon during surgery. For example, the displays 50, 50a can convey an error message to the user when the change Δβ in therelative angle β exceeds the desired angular correction, when theengagement features 40, 40 a detect that they are not attached to thecorrect surgical device, and/or when engagement between the engagementfeatures 40, 40 a and the pedicle screws 70, 70 a has been lost orweakened. In some embodiments, where the processors 22, 22 a areconfigured to calculate the rate of change Δβ/Δt in the relative angleβ, the displays 50, 50 a can convey an error message to the user whenthe rate exceeds a predetermined speed limit. In still furtherembodiments, should the patient be rotated in the axial plane during thesurgery, for example due to a table rotation or rolling over of thepatient, one or both of the modules 10, 10 a can detect the change andcan be configured to alert the surgeon via an error message on thedisplays 50, 50 a, which may include an instruction to recalibrate. Incase of a need to recalibrate, the modules 10, 10 a can be detached fromthe screws 70, 70 a and can be attached to one another to repeat thecalibration procedure described above.

Information detected and/or calculated by the modules 10, 10 a duringthe procedure can be collected and stored for later use. The informationcan be stored locally in the memories 24, 24 a and/or can be transmittedvia the communications interfaces 26, 26 a to one or more external basestations. The stored information can be used at a later time for variouspurposes, for example to create a reproduction of the surgery, forclinical improvement, research, and/or ethnography.

Another exemplary pedicle subtraction osteotomy using one or moresurgical electronic modules as described herein is illustrated in FIGS.7-8. The procedure according to this method involves the use of foursurgical electronic modules 10 b, 10 c, 10 d, 10 e, which can detect,calculate, store, and/or transmit information in a similar manner to themodules 10, 10 a described above during the exemplary pediclesubtraction osteotomy of FIGS. 4-6. It will be appreciated by a personskilled in the art that any surgical electronic module as describedherein can be used, either the same or different from one another, andthat the modules 10 b, 10 c, 10 d, 10 e can be used in a variety ofsurgical procedures that effect changes in anatomical position and/ororientation.

Similarly to the procedure described with reference to FIGS. 4-6, adesired angular correction of the spine can be determined prior to thesurgery. The modules 10 b, 10 c, 10 d, 10 e can be calibrated by freelyrotating mated pairs of the modules 10 b, 10 c, 10 d, 10 e until enoughpositional information has been acquired to synchronize their coordinatesystems. For example, the module 10 b can be attached to each of theother modules 10 c, 10 d, 10 e, and synchronized with each of the othermodules 10 c, 10 d, 10 e to ensure that all of the modules 10 b, 10 c,10 d, 10 e are synchronized to each other.

The first three modules 10 b, 10 c, 10 d can be rigidly attached tothree pedicle screws 70 b, 70 c, and 70 d, while the fourth module 10 dcan be rigidly attached to a surgical cutting instrument such as arongeur 90. The engagement features 40 b, 40 c, 40 d, 40 e can detect anidentity of the device to which the modules 10 b, 10 c, 10 d, 10 e areattached, such that the first three modules 10 b, 10 c, 10 d can detectthat they are each attached to a pedicle screw and the fourth module 10e can detect that it is attached to a rongeur. Based on thisinformation, the first three modules 10 b, 10 c, 10 d can switch intothe orientation detection mode in which only orientation information isdisplayed to the user, and the fourth module 10 e can switch into thefull detection mode in which orientation and position information isdisplayed. Further, as explained in detail below, the processors 22 b,22 c, 22 d of the first three modules 10 b, 10 c, 10 d can be configuredto calculate different positional information from the processor 22 e ofthe fourth module 10 e. It will be appreciated by a person skilled inthe art, however, that the procedure can be performed utilizing onlythree modules, two of which are attached to two pedicle screws and thethird of which is attached to a surgical cutting instrument.

The pedicle screws 70 b, 70 c, 70 d can be implanted into pedicles P1,P2, and P3 on vertebrae V1, V2, and V3, either before or after themodules 10 b, 10 c, 10 d are attached thereto. At least one of thepedicle screws 70 b, 70 c, 70 d can be implanted on an opposite side ofan intended osteotomy site O from at least one of the other pediclescrews 70 b, 70 c, 70 d. Similarly to the modules 10, 10 a used in theexemplary procedure of FIGS. 4-6, an initial position and/or orientationof the modules 10 b, 10 c, 10 d with respect to one another can be setby actuating the zeroing buttons 60 b, 60 c, 60 d. Thus, as shown inFIG. 7, the displays 50 b, 50 c, 50 d can each display “0” to indicatethat the modules 10 b, 10 c, 10 d are oriented at an initial anglerelative to one another. Angular correction of the spine along thesagittal plane can then be performed according to customary surgicalprocedures, which can include removal of bone from a vertebra disposedbetween the second and third vertebrae V2, V3 by the rongeur 90. Duringthe procedure, the sensors 22 b, 22 c, 22 d can continually detectabsolute azimuth and polar angles θ, φ of each of the modules 10 b, 10c, 10 d. The modules 10 b, 10 c, 10 d can communicate their absoluteazimuth and polar angles θ, φ with each other (e.g., via Bluetooth orother wired or wireless communication) to thereby allow for theprocessors 22 b, 22 c, 22 d to calculate a relative angle β₁ of thefirst module 10 b with respect to the second module 10 c, a relativeangle β₂ of the second module 10 c with respect to the third module 10d, and a relative angle β₃ of the first module 10 b with respect to thethird module 10 d. Further, the modules 10 b, 10 c, 10 d can calculatechanges Δβ₁, Δβ₂, Δβ₃ in the relative angles β₁, β₂, β₃ throughout theprocedure, rates of changes Δβ₁/Δt, Δβ₂/Δt, Δβ₃/Δt and/or rates ofchanges Δθ/Δt, Δφ/Δt in the azimuth and polar angles θ, φ of each of themodules 10 b, 10 c, 10 d.

Because the relative angle β₁ of the modules 10 b, 10 c with respect toone another does not change throughout the procedure since the modules10 b, 10 c are on the same side of the osteotomy site O, the modules 10b, 10 c, 10 d can be configured to display only Δβ₂. The displays 50 b,50 c, 50 d can be configured not to display the change Δβ₁ since it willremain substantially equal to zero throughout the procedure, and not todisplay the change Δβ₃ because Δβ₂ and Δβ₃ will remain substantiallyequal to one another throughout the procedure. Of course, it will beappreciated by a person of skill in the art that the modules 10 b, 10 c,10 d could display either Δβ₂ and Δβ₃, since they are substantiallyequal to one another, and Δβ₂ has been chosen solely for purposes ofillustration. Also, if at any point during the surgery, Δβ₁ ceases to besubstantially equal to zero and/or Δβ₂ and Δβ₃ cease to be substantiallyequal to one another, all three relative angular changes Δβ₁, Δβ₂, Δβ₃can be displayed on the displays 50 b, 50 c, 50 d. Any of these valuescan be displayed on an external display alternatively or in addition.

The module 10 e can be attached to the rongeur 90 via engagementfeatures 40 e on the module 10 e at any point during the surgery to helpthe surgeon remove a desired amount of bone from a desired location.Like the modules 10 b, 10 c, 10 d, the module 10 e can be “zeroed” byuser actuation of the zeroing button 60 e when the module 10 e is placedin an initial position and/or orientation, e.g., when the rongeur 90 towhich the module 10 e is coupled is inserted at a desired cutting angleand at a maximum desired cutting depth into the patient's body. Thus, asshown in FIG. 7, the module 10 e can display two zeros, one indicatingan initial angle and one indicating an initial distance. Preferably, themodule 10 e is zeroed before any angular correction in the patient'sspine has been achieved and/or at the same time that the other modules10 b, 10 c, 10 d are zeroed.

Because the module 10 e is able to detect that it is attached to asurgical instrument, e.g., the rongeur 90, as opposed to a surgicalimplant, e.g., the pedicle screws 70 b, 70 c, 70 d, it can be configuredto calculate and/or display different positional information than themodules 10 b, 10 c, 10 d. This information can supplement theinformation displayed by the modules 10 b, 10 c, 10 d to confirm that adesired angular correction has been achieved. In particular, whereas themodules 10 b, 10 c, 10 d are configured to calculate and/or displaychanges in positional information with respect to one another, themodule 10 e can be configured to calculate and/or display changes in itsown positional information throughout the surgery. Further, whereas themodules 10 b, 10 c, 10 d are configured to calculate and/or displaychanges in their relative orientations, the module 10 e can beconfigured to calculate and/or display changes in both orientation andposition.

To perform these calculations, the module 10 e can continually detectabsolute azimuth and polar angles θ, φ of the module 10 e with thesensor 28 e, calculate an absolute angle β₄ of the module 10 e in thesagittal plane with the processor 22 e, and store the absolute angle β₄for any given time in the memory 24 e. Similarly, the sensor 28 e cancontinually detect an absolute position (e.g., including a distance d₄of the module 10 e relative to a starting position) via triangulation,time-of-flight, or other positioning algorithms using ultrasonic,electromagnetic, and/or infrared location signals sent by each of themodules 10 b, 10 c, 10 d, 10 e and communicated therebetween. It will beappreciated by a person skilled in the art that, where at least threemodules are used, unique position information can be created throughlocation signals sent out by each of the modules and communication amongall of the modules of the information received from the signals whilethe modules 10 b, 10 c, 10 d are stationary, e.g., before they are movedtogether as part of reduction procedure. It will further be appreciatedby a person skilled in the art that the position of the rongeur 90 canbe determined through communication between the module 10 e and othersurgical electronic modules positioned in the operating room. As theposition and/or orientation of the rongeur 90 changes during surgery,the processor 22 e can calculate and the display 50 e can display achange Δβ₄ in the angle P₄ and/or a change Δd₄ in the distance d₄ of themodule 10 e—and therefore of the rongeur 90—in the sagittal plane. Forexample, as shown in FIG. 8, the display 50 e can indicate that therongeur 90 has moved by a distance of 49 mm and by an angle of 27degrees from the initial position and orientation. In this way, thesurgeon can know when the rongeur 90 has completed a desired motion tothereby remove a desired amount of bone. In some embodiments, the module10 e can be configured to alert the surgeon when the rongeur 90 is movedoutside of or beyond a surgical plane, e.g., beyond a desired angleand/or distance, for example by displaying an error message on thedisplay 50 and/or providing an audio signal or vibration. For example,the surgeon can be warned when the distal end of the rongeur isapproaching or has exceeded a predetermined maximum insertion depth inthe anterior direction (e.g., when the axial displacement of the rongeurrelative to the starting position approaches zero or becomes negative).

Similarly to the exemplary pedicle subtraction osteotomy of FIGS. 4-6,when the desired angular correction of the spine in the sagittal planehas been achieved, the change Δβ₂ in the relative angle 13 ₂ displayedon the displays 50 b, 50 c, 50 d will be equal to the desired angularcorrection. The patient's spine can then be stabilized in the correctedposition via a spinal fixation element 80 that can be attached to theimplanted pedicle screws 70 b, 70 c, 70 d. The modules 10 b, 10 c, 10 dcan be removed from the pedicle screws 70 b, 70 c, 70 d and the module10 e can be removed from the rongeur 90 either before or after fixationwith the spinal fixation element 80.

It will be appreciated by a person skilled in the art that a greaternumber of modules can enhance the accuracy of the procedure by providingfor a greater amount of positional information. For example, using moremodules can provide positional information to a greater degree ofprecision and/or specificity, e.g., with more significant digits, whichcan be displayed to the surgeon. As each module is added in theprocedure, the number of significant digits displayed to the surgeon canincrease, thereby providing a measure of the increase in accuracy addedby each additional module to the surgeon. Additionally or alternatively,using a greater number of modules can enable the modules to detectand/or calculate their positions and/or orientations in more dimensions.The positions, orientations and/or changes in the positions and/ororientations of the modules can be displayed to the user for each planein which information is acquired. However, it will also be appreciatedby a person of skill in the art that a position and/or an orientation ofthe module in certain planes need not be calculated since it can beassumed that the patient will not move in certain planes.

It will further be appreciated by a person skilled in the art that thedevices and methods described herein can be particularly useful forrobotic assisted surgery. For example, one or more surgical electronicmodules as described herein can transmit positional information to arobotic manipulator, which can manipulate the one or more modules untilthey have reached a desired final position that has been input to themanipulator.

Although the invention has been described by reference to specificembodiments, it should be understood that numerous changes may be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedescribed embodiments, but that it have the full scope defined by thelanguage of the following claims.

The invention claimed is:
 1. A surgical method for measuring a change inanatomical position or orientation, comprising: mechanically connectinga first electronic module to a second electronic module; synchronizing acoordinate system of the first electronic module with a coordinatesystem of the second electronic module while the first and secondelectronic modules are mechanically connected to one another; rigidlyattaching the first electrode module to a first surgical device; rigidlyattaching the second electronic module to a second surgical device;detecting an absolute angle with respect to the earth of the firstelectronic module attached to the first surgical device by a sensor ofthe first electronic module, the first surgical device being operativelycoupled with a first vertebra of a patient; detecting an absolute anglewith respect to the earth of the second electronic module attached tothe second surgical device by a sensor of the second electronic module,the second surgical device being operatively coupled with a secondvertebra of the patient; removing bone between the first and secondvertebrae at an osteotomy site to cause movement of at least one of thefirst and second electronic modules; calculating by a processor of atleast one of the first and second electronic modules a change in anangle of the first electronic module with respect to the secondelectronic module multiple times during a surgery to determine a changein an angle of the first surgical device with respect to the secondsurgical device; and conveying to a user the change in the angle of thefirst surgical device with respect to the second surgical device tothereby assist the user in determining a change in an angle of the firstvertebra with respect to the second vertebra.
 2. The surgical method ofclaim 1, wherein the method further comprises actuating reset mechanismsof the first and second electronic modules to set an initial angle to beused in calculating the change in the angle of the modules relative toone another.
 3. The surgical method of claim 1, wherein the methodfurther comprises repeating the calculating and conveying steps until atarget position or orientation of the first surgical device with respectto the second surgical device has been reached.
 4. The surgical methodof claim 3, wherein the method further comprises alerting the user whenthe target position or orientation has been reached.
 5. The surgicalmethod of claim 1, wherein the method further comprises calculating arate of the change in the angle of the first surgical device withrespect to the second surgical device.
 6. The surgical method of claim1, wherein the change in the angle of the first surgical device withrespect to the second surgical device is conveyed to the user on adisplay of at least one of the first electronic module and the secondelectronic module.
 7. The surgical method of claim 1, wherein: the firstsurgical device is a first bone screw implanted in the first vertebra;and the second surgical device is a second bone screw implanted in thesecond vertebra.
 8. The surgical method of claim 7, further comprisinglocking a spinal rod to the first and second bone screws after a targetposition or orientation of the first vertebra with respect to the secondvertebra has been reached.
 9. The surgical method of claim
 1. whereinsynchronizing the coordinate system of the first electronic module andthe coordinate system of the second electronic module includes rotatingthe first and second electronic modules through space as a pair.
 10. Thesurgical method of claim 1, further comprising: identifying a surgicalinstrument device type of the first surgical instrument after rigidlyattaching the first electrode module to the first surgical device usingan engagement feature of the first electronic module that is configuredto interface with a device identifier on the first surgical instrument.11. The surgical method of claim 1, further comprising: rigidlyattaching a third electronic module to a surgical cutting instrument;detecting positional information of the third electrode module attachedto the surgical cutting instrument by a sensor of the third electronicmodule; and conveying to a user any of cutting angle and cutting depthcalculated by a processor of the third electronic module based on thedetected positional information; wherein removing bone between the firstand second vertebrae at an osteotomy site is performed using thesurgical cutting instrument.
 12. A surgical method for measuring achange in anatomical position or orientation, comprising: mechanicallyconnecting a first electronic module to a second electronic module;synchronizing a coordinate system of the first electronic module with acoordinate system of the second electronic module while the first andsecond electronic modules are mechanically connected to one another;rigidly attaching the first electronic module to a first surgicaldevice; rigidly attaching the second electronic module to a secondsurgical device; detecting an absolute angle with respect to the earthof the first electronic module attached to the first surgical device bya sensor of the first electronic module, the first surgical device beingoperatively coupled with a first portion of a patient's anatomy;detecting an absolute angle with respect to the earth of the secondelectronic module attached to the second surgical device by a sensor ofthe second electronic module, the second surgical device beingoperatively coupled with a second portion of a patient's anatomy;calculating by a processor of at least one of the first and secondelectronic modules a change in an angle of the first electronic modulewith respect to the second electronic module multiple times during asurgery to determine a change in an angle of the first surgical devicewith respect to the second surgical device; and conveying to a user thechange in the angle of the first surgical device with respect to thesecond surgical device to thereby assist the user in determining achange in an angle of the first portion of the patient's anatomy withrespect to the second portion of the patient's anatomy; wherein thechange in the angle of the first surgical device with respect to thesecond surgical device is conveyed to the user on a display of at leastone of the first electronic module and the second electronic module. 13.The surgical method of claim 12, wherein the method further comprisesactuating reset mechanisms of the first and second electronic modules toset an initial angle to be used in calculating the change in the angleof the modules relative to one another.
 14. The surgical method of claim12, wherein the method further comprises repeating the calculating andconveying steps until a target position or orientation of the firstsurgical device with respect to the second surgical device has beenreached.
 15. The surgical method of claim 14, wherein the method furthercomprises alerting the user when the target position or orientation hasbeen reached.
 16. The surgical method of claim 12, wherein the methodfurther comprises calculating a rate of the change in the angle of thefirst surgical device with respect to the second surgical device. 17.The surgical method of claim 12, wherein: the first portion of thepatient's anatomy is a first vertebra and the first surgical device is afirst bone screw implanted in the first vertebra; and the second portionof the patient's anatomy is a second vertebra disposed opposite anosteotomy site from the first vertebra and the second surgical device isa second bone screw implanted in the second vertebra.
 18. The surgicalmethod of claim 17, further comprising locking a spinal rod to the firstand second bone screws after a target position or orientation of thefirst vertebra with respect to the second vertebra has been reached. 19.The surgical method of claim 12, wherein synchronizing the coordinatesystem of the first electronic module and the coordinate system of thesecond electronic module includes rotating the first and secondelectronic modules through space as a pair.
 20. The surgical method ofclaim 12, further comprising: identifying a surgical instrument devicetype of the first surgical instrument after rigidly attaching the firstelectronic module to the first surgical device using an engagementfeature of the first electronic module that is configured to interfacewith a device identifier on the first surgical instrument.
 21. Thesurgical method of claim 12, further comprising: rigidly attaching athird electronic module to a surgical cutting instrument; detectingpositional information of the third electronic module attached to thesurgical cutting instrument by a sensor of the third electronic module;and conveying to a user any of cutting angle and cutting depthcalculated by a processor of the third electronic module based on thedetected positional information; wherein removing bone between the firstand second vertebrae at an osteotomy site is performed using thesurgical cutting instrument.